Question: Something is wrong with our apricots. The tree looks good, but the fruit are severely damaged. This is all over the tree. Leaves seem to be fine. Ideas? — Question submitted via Bernalillo County Extension Agent Sara Moran
Answer: That stippled look on the surface of your apricots looks like it could be frost burn from last week. Sometimes tiny fruit turn a dull grey, shrivel up, and fall to the ground without any frost damage at all. This phenomenon, called fruit drop, is fairly normal. I got a question about this from Sierra County Extension Agent Sara Marta two weeks ago.
Potential reasons for fruit drop include poor pollination or heavy fruit load. Fruit trees often produce way more flowers than they can actually support if they were to all grow into full-sized fruit, so the tree is doing some natural thinning. Because fruit drop is so common, thinning fruit manually should be done after fruit drop.
Once frost danger, fruit drop, and our heavy winds have passed (maybe another month?), it is recommended that fruit be thinned to about 2–4 inches between every single fruit on each branch. This sounds extreme, but it’s the recommended method. For more on the importance of fruit thinning and demo videos, check out my column from 2018 by visiting the blog at nmsudesertblooms.blogspot.com and searching the term “thinning.”
Question: I have a client that is worried her tree is sick. She moved here in December and does not know the history of the tree and is looking for recommendations on what to do.
— Question submitted via Curry County Extension Agent Mason Grau
Answer: From close up, this tree does look stressed. And from afar I can begin to imagine why. Even though there’s beautiful shredded bark mulch surrounding the root area, I can see the glimmer of black plastic mulch right around the base of the trunk. Mulch is great at helping to maintain soil moisture, but only if moisture can get down into the ground.
I’m not exactly sure what the problems are, but some more information could be helpful. For any homeowner that’s starting to notice potential problems, this is a great time to reassess irrigation techniques and check to be sure the tree isn’t planted too deeply.
Questions to ask yourself that might lead to the primary problem include: How are the trees currently watered? What’s the frequency? What’s the method (sprinkler, hose, drip, etc.)? What’s the length of time water is applied? And where is the water being applied? We’re trying to get roots to grow 2–3 feet deep and to extend out laterally, well beyond the canopy drip line, so that’s where we need to be watering.
Any black plastic should be pulled back dramatically, if not entirely, so the roots can get the two things they need: oxygen and water. Another question: Has any fertilizer been applied? No fertilizer is recommended; I just want to be sure we’re not seeing fertilizer burn symptoms.
Sometimes crispy leaf margins are a sign of salt stress. I wrote a column explaining salt burn in roses. If this is the main problem, watering to a deeper depth a few times can help move the salts lower in the soil profile and out of the root zone. Visit the blog (URL listed above) and search “salt” for more on that.
I’m afraid this poor tree was poorly installed and has not been cared for. It may also be planted too deep. The trunk flare (aka root flare) should be visible above ground, so take the time to gently dig a little at the base of the trunk, remove some of that soil, and see if you can uncover and expose the flare.
The nearby turf looks great, which implies that it’s being watered regularly. However, trees planted in or near turf often don’t get enough water, even if the turf is watered several times per week. After pulling back the black plastic, I suggest applying water to the tree root area “low and slow” (meaning a slow trickle so it saturates deeply without running off) with a hose and moving the hose to different parts of the root zone. I
f it’s on a slow trickle, maybe 1 hour will suffice. It depends largely on soil type, so I’d suggest leaving it on to soak for 20–30 minutes the first time. Then a few hours after it’s turned off, go out with a shovel or spade and dig down a little to see how deep the water got. If it’s moist only 1 foot deep, double the watering time.
For mature desert-adapted trees, water to a depth of 2–3 feet once or twice a month right now and increase to two or four times per month in summer. The frequency depends partly on how hot and windy the weather is, but also on soil type and tree species. Be sure root zones are drying slightly between irrigations.
Believe it or not, many urban plants struggle from over-watering. Yes, even in New Mexico. I’ll include links to more information on irrigating and not planting trees too deep on the blog (again, nmsudesertblooms.blogspot.com/).
Watch the new growth as the season progresses; if new leaves look green and healthy with increased water then we may have solved the problem!
Another issue altogether is that Bradford pears are not generally recommended for New Mexico landscapes. There are many other tree species that are more likely to thrive in our region without needing as much water. A few that come to mind are desert willow, Chinese pistache, Texas red oak, lacebark elm, and New Mexico olive.
(For more gardening information, including decades of archived Southwest Yard & Garden columns, visit the NMSU Extension Horticulture page (desertblooms.nmsu.edu), follow us on social media (@NMDesertBlooms), or contact your County Extension office (aces.nmsu.educounty).
Marisa Thompson, PhD, is the extension horticulture specialist for New Mexico State University and is based at the Agricultural Science Center at Los Lunas.)